Electrical heating unit.



C. E. CHANEY. ELECTRICAL HEATING UNIT.

APPLICATION man was 19. 1916.

1,206,5 1 O. Patented Nov. 28, 1916.

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PATENT oFrioE.

CARYL E. CHANEY, 0F DETROIT, lVIICI-IIGAN.

ELECTRICAL HEATING UNIT.

Specification of Letters Patent.

Patented Nov. 28, 1916.

Application filed June 19, 1916. Serial No. 104,364.

To all whom it may concern Be it known that I, CARYL E. CI-IANEY, acitizen of the United States of America, residing at Detroit, in thecounty of lVayne and State of Michigan, have invented certain new anduseful Improvements in Electrical Heating Units, of which the followingis a specification, reference being had therein to the accompanyingdrawings.

. The invention relates to electrical heating units of the armoredresistor type, and it is the object of the invention to obtain variousfeatures of advantage as hereinafter set forth.

In the drawings: Figure 1 is a sectional elevation of the unit; Fig. 2is a crosssection thereof;'Fig. 3 is an'enlarged' crosssection throughthe refractory tube on which the resistor is wound; Fig. 4 is anelevation thereof; and Fig. 5'is an elevation of the unit connected intoan electric circuit.

My improved construction of heating unit is more particularly designedfor use where it is desirable to limit the temperature in all parts ofthe unit, so as to avoid danger of ignition of explosive vapors, or forother reasons. It is also an object to obtain a construction in whichthe maximum heat distribution. may be obtained. with'n given spacelimits, and without exceeding the predetermined temperature. The unit isthercfore preferably in the form of a hollow tube, dissipating heat bothinternally and externally, the internal heat being distributed byconvection and the external heat by radiation and convection.

In detail, A is av tubular refractory insulator body on which theheating resistor B is wound. This body is preferably formed ofporcelain, but inasmuch as such material is e sily cracked by unequaltemperatures in different portions thereof, special provision is madefor avo ding this objection. Preferably the tubeis formed of apluralityof segments, said segments being preferably not greater than an angle of120, so as to limit the difference in length of their ini ternal andexternal arcs. As shown, the segments B B etc, are provided with atongue and groove or lapped edge engagement C, so as to hold them fromrelative displacement. Externally, the segments are threaded andpreferably with a double thread, so that the resistor may be wound inone groove or thread to extend continuously from one end of the tube tothe other, and then be wound in the intermediate groove to extend backto the starting end. This arrangement is desirable, as i neutralizes anyobjectionable inductive effect.

The unit armored both internally and externally, preferably withmetallic tubing. The segments B B etc. are placed around the inner tubeI), but are preferably separated therefrom by thermal insulation D. Theouter tube E surrounds these segments B B etc, and a plastic filling Fof an electrically insulating material having relativcly high thermalconductivity is placed between these segments and the outer tube. Thereason for this construction is that the outer surface being greater inextent than the inner surface, there is a tendency for the latter torise in temperature, which is avoided by the thermal insulation whichslows the rate of conduction.

To complete the unit, caps G and G are arranged at the opposite ends ofthe unit to engage inner and outer tubes D and F. The terminals H and Hextend out through one of these caps, being insulated by suitablebushings I and I. As shown, the terminals are in the form of threadedstuds, to which contact blades J and J are attached, the latter beingadapted for insertion into an insulated holder K for the mainconductors.

In use, the units may be mounted to extend perpendicularly to the memberK and parallel to the wall L of the oven or chamber to be heated. Whencurrent is supplied, the heat will be dissipated both externally andinternally, the internal heat being distributed by circulatory aircurents, as indicated by the arrows.

What I claim as my invention is 1. An electrical heating unit,comprising a tubular core member formed of a refractory insulatingmaterial formed in segments, said core being provided with a doublethread or groove therein, a resistor wound in said thread to extend fromone end to the other of the tube and to return in the intermediategroove to the original end, and an internal and external armor for saidtube.

2. An electrical heating unit, comprising an inner armor tube, aninsulator tube formed in segments placed about said inner armor tube andin contact therewith, a resistor wound upon said segmental insulatortube, an outer armor tube, and a refractory, solidified plasticinsulation between the resistor and the outer tube.

3. An electrical heating unit, comprising an inner armor tube, arefractory insulator tube formed of segments placed about said innerarmor tube, said segments having complementary grooves forming a spiralthread thereabout, a resistor Wound in said thread, an outer armor tube,and a solidified plastic insulator between said resistor and outer tube.

4. An electrical heating unit, comprising an inner armor tube, aninsulator tube formed in segments arranged about said inner armor tube,said segments being provided externally with grooves formingcomplementary portions of a double thread, a resistor wound in saidgrooves from one end of the tube to the other and returning through anintermediate groove, an outer armor tube, and solidified plasticinsulation between said resistor and outer tube.

5. An electrical heating unit, comprising an inner armor tube, aninsulator tube formed in segments arranged about said inner armor tube,said segments being provided externally with grooves formingcomplementary portions of a double thread, a resistor Wound in saidgrooves from one end of the tube to the other and returning through anintermediate groove, an outer armor tube, and means for decreasing thethermal conductivity to the inner tube in relation to the thermalconductivity to the outer tube to equalize the temperatures thereof.

6. An electrical heating unit, comprising an inner armor tube, aninsulator tube arranged about said armor tube, thermal insulationbetween said tubes, a resistor Wound upon said insulator tube, an outerarmor tube and electrically insulating material having relatively highthermal conductivity between said armor tube.

In testimony whereof I affix my signature.

CARYL E. CHANEY.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, I). C.

insulator tube and outer

